Under normal drying conditions, concrete (e.g., Portland cement concrete with or without pozzolans mixed therein) will shrink from the exposed surfaces inward as it desiccates and hardens. The amount of drying shrinkage typically ranges between approximately 0.0002 to approximately 0.0008 inches per inch with approximately 0.0005 inches per inch being the norm. Significantly, the drying shrinkage does not occur through the full depth of the concrete, but is rather rapidly attenuated to insignificance only a few inches from the exposed surfaces. Since the top is typically the only surface of a concrete slab exposed to drying, it is normal for a downwardly decreasing shrinkage gradient to develop within the uppermost few inches of a slab. As a result of such shrinkage gradient, the top region of a concrete slab tends to “curl” (i.e., develop an upward facing concave curvature) as it dries. This is not a desirable condition, since a measure of quality in a concrete slab is its surface flatness.
The problems associated with curling concrete slabs are exacerbated at concrete “joints” formed at sawcuts. Such sawcuts are made at the surface of a slab to control cracking within the slab, or are made at the surface of two adjacent slabs. Specifically, a sawcut's surface edges are subject to spalling as traffic moves over slab joints.